The simplest option for toning down overly darkened hair is to wash the area with a clarifying shampoo that has a drying effect. This method would strip away some of the color, leaving behind a lighter shade. Another alternative is to create a homemade solution by mixing 1 teaspoon of baking soda into an everyday shampoo. Lather it in, then wait 15 minutes before rinsing.
Washing with clarifying shampoo can sufficiently lighten hair dyed in brunette and red shades. If shampooing doesn't produce the desired effect, mask the dark hair with highlights to tone down the color. Professional hairstylists can also adjust the color one or two levels using a soap cap. Those with salon experience can create a soap cap at home, which involves mixing clarifying shampoo, conditioner and a small amount of prepared bleach. This solution would be applied to the hair and must sit for 15 minutes before washing.
Another option is to strip the dye from the hair and start over. Color removal kits are available at beauty supply stores and can be used at home. They contain a mild solution designed to strip the artificial color without ruining the hair's natural pigment, making removal kits less damaging and more reliable than harsh bleach. While bleach lightens dyed hair, it is generally less effective on darker shades and sometimes has the unintended consequence of producing a completely new hair color.